In a long-term evolution (LTE) system, a base station (BS) allocates resource information to user equipment (UE) needed by it in transmitting or receiving data, comprising information on uplink shared channel resources and information on physical hybrid ARQ indicator channel (PHICH) used by the UE in transmitting uplink data, and then the BS notifies the resource information to the UE; hence, the UE may use the allocated uplink resources to transmit uplink data, and detect information on downlink feedback acknowledgement (ACK)/negative acknowledgement (NACK) at a corresponding PHICH; wherein ACK denotes that data is correctly received, and NACK denotes that data is wrongly received.
In the implementation of the present invention, the inventors found that there existed following problem: after the BS preliminarily allocates uplink resources to each piece of UE, when PHICH resources are allocated to each piece of UE, a problem that different pieces of UE indicate the same PHICH resource will possibly occur, thereby resulting in collision of the PHICH resources; in such a case, the BS does not allocate resource information to those pieces of UE where collision occurs, leading to that the pieces of UE cannot upload data, or the BS adjusts an index of the minimal uplink resource block of the UE, bringing limit to the scheduling algorithm.
Collision of PHICH resources will be described below by way of examples.
For Rel.8, as the number of available PHICHs is less than the number of physical resource blocks (PRBs) in the system, collision of PHICHs will inevitably occur.
Refer to Table 1, in which cases where minimal PRB indices Ilowest-index from 0 to 35 are illustrated only.
TABLE 1I_lowest0123456789101112131415. . .26272829303132333435n(group)0123012301230123. . .2301230123n(serial number)0000111122223333. . .6677770000
For example, for a 10 MHz system, the number of the PRBs is 50, and it is assumed that the number of the available downlink PHICHs is 32; if the lowest PRB index allocated preliminarily by the BS to UE1 is Ilowest-index=0, and the number of the virtually continuously allocated PRBs is 5, then it can be seen from Table 1 that the PHICH resource that can be allocated by the BS to the UE1 is PHICH (0,0); and for UE2, if the lowest PRB index Ilowest-index=32, and the number of the virtually continuously allocated PRBs is 5, then it can be seen from Table 1 that the PHICH resource that can be allocated by the BS to the UE2 is also PHICH (0,0). Therefore, even though the lowest resource blocks of the UE1 and UE2 are different, the PHICH resources are identical, the identical PHICH resources allocated to different pieces of UE being referred to herein as collision of PHICH resources. Hence, the BS does not notify the resource information to the UE2, causing that the UE2 cannot upload data, or the BS adjusts an index of the minimal uplink resource block of the UE, bringing limit to the scheduling algorithm.
In Rel.8, in order to solve the above problem, a value n (DM_RS) to which a 3-bit uplink demodulation_reference symbol (DM_RS) cyclic shift corresponds and a lowest PRB index are cooperatively used to instruct PHICH resource. In this way, for an uplink PUSCH channel, there are 8 PHICH channels available, and the BS, for the comprehensive consideration, may allocate different PHICH resources to UE in which collision is possible to occur, thereby alleviating the possibility of collision to a certain extent. Refer to tables 2a and 2b, in which relationship between a lowest PRB index, an index of a PHICH group and n (DM_RS) is shown in Table 2a, and relationship between a lowest PRB index, the sequence index within the group of PHICH and n (DM_RS) is shown in Table 2b.
n(group)I(lowest_index, PRB_RA)n(DM_RS)0123456789101112131415. . .262728293031323334352a00123012301230123. . .230123012311230123012301230. . .301230123022301230123012301. . .012301230133012301230123012. . .123012301240123012301230123. . .230123012351230123012301230. . .301230123062301230123012301. . .012301230173012301230123012. . .1230123012n(seq, PHICH)I(lowest_index, PRB_RA)n(DM_RS)0123456789101112131415. . .262728293031323334352b00000111122223333. . .667777000011111222233334444. . .770000111122222333344445555. . .001111222233333444455556666. . .112222333344444555566667777. . .223333444455555666677770000. . .334444555566666777700001111. . .445555666677777000011112222. . .5566667777
For example, if the lowest PRB index allocated preliminarily by the BS to UE1 is Ilowest-index=0, and the number of the virtually continuously allocated PRBs is 5, then it can be seen from tables 2a and 2b that when the n (DM_RS)=0, PHICH resource that can be allocated by the BS to the UE1 is PHICH (0,0); and for UE2, if the lowest PRB index Ilowest-index=32, the number of the virtually continuously allocated PRBs is 5, and the n (DM_RS)=0, then it can be seen from tables 2a and 2b that the PHICH resource that can be allocated by the BS to the UE2 is also PHICH (0,0). Thus, collision of PHICH resources occurs. At present, in order to solve the above problem of collision of PHICH resources, the BS may select different n (DM_RS) values for the UE2. For example, the BS may select one of n(DM_RS)=1˜7 having an idle PHICH, such as n(DM_RS)=1. At this moment, it can be seen from tables 2a and 2b that the PHICH resource that is allocated to the UE2 is PHICH (1,1), thereby alleviating occurrence of collision to a certain extent.
Although collision may be avoided by using the above manner, it can be seen from tables 2a and 2b that there are only seven n (DM_RS) values available for allocation. Therefore, in the versions of Rel.10 and later, due to carrier aggregation, multiple-input multiple output (MIMO) and other cases possibly occur, the probability of collision exceeds an acceptable extent.
It should be noted that the cause of occurrence of PHICH collision is not due to insufficient PHICH resources (the number of PHICHs configured by the system is not less than the number of the pieces of the uplink UE), and collision is possible to occur when there are relatively sufficient PHICH resources.
For example, for a 10 MHz system, the number of the PRBs is 50, and it is assumed that the number of the available PHICHs is 32; it can be seen from tables 2a and 2b that the number of table sets available for 50 PRBs is 4, which are table—0, table 1, table 2 and table 3, respectively, each table set denoting the case of use of the PHICHs. Table—0 and table—1 are only shown below.
Currently, according to the agreement between the BS and the UE, the table set used by the BS in allocating PHICH resources to the UE is one of table—0, table—1, table—2 and table 3, for example, table—0.
If the PHICH resource allocated by the BS to the UE1 is PHICH (0,0), when the PHICH resource allocated by the BS to the UE2 is PHICH (0,0), the BS may allocate to the UE2 one of the idle PHICH resources to which (DM_RS)=1-7 correspond so as to avoid collision; and if all the PHICH resources in table—0 are used, the BS cannot allocate the PHICH resources to the UE2 at present, even if there exist idle PHICH resources in any one of other table sets, such as table—1, table—2 and table—3. Therefore, PHICH collision will inevitably occur, thereby finally resulting in that the UE2 cannot transmit uplink data or the scheduling is limited.
Refer to tables 4a and 4b for cases of collision, in which the PUSCH lowest with Ilowest-index=0, 5, 10, 15, 16, 21, 26, 31, 32, 37, 42, 47, 48 uses a table set, such as table—0; for the use after the ninth one in that table set, collision will inevitably occur, and even if other table sets are idle, collision will occur.
TABLE 4an(group)I(lowest_index, PRB_RA)n(DM_RS)0510151621263132374247480012301230123011230123012301223012301230123301230123012340123012301230512301230123016230123012301273012301230123
TABLE 4bn(seq, PHICH)I(lowest_index, PRB_RA)n(DM_RS)0510151621263132374247480012345670123411234567012345223456701234563345670123456744567012345670556701234567016670123456701277012345670123
Following documents are listed below for easy understanding of the present invention, which are incorporated herein by reference, as they are set forth in this text.
1) U.S. Pat. No. 7,414,989, ACK/NACK determination reliability for a communication device; and
2) UE6813261, Method of mobile communication and apparatus therefor.